Paper manufacturing



30, 1939- s. CARROLL Re. 21,098

PAPER MANUFACTURING Original Filed Jan. 11, 1936 L5, filzmo, W r GQ.

ATTORNEY.

Reissued May 30, 1939 PATENT OFFICE PAPER, MANUFACTURING George 8.Carroll, Bennington, N. H.

0riginal No. 2,064,647, dated December 15, 1936,

Serial No. 58,724, January 11, 1936. Application for reissue July 15,1938, Serial No. 219,469

7 Claims.

This invention relates to improvements in paper manufacture and isdirected more particularly to improvements in apparatus for and methodsof drying paper.

The principal objects of the invention are the provision of methods ofdrying paper to facilitate the making of paper having both its surfacesmore nearly uniform than has heretofore been possible.

The type of dryer with which the invention is illustrated includes aplurality of rotatable spaced hollow drying cylinders, commonly calledcans, which are arranged in upper and lower banks or rows. A heatingmedium such as steam is delivered into the cylinders and the condensateis led therefrom.

The web of paper to be dried is led into the wet end of the machine andit travels over a roll of one bank or row and then over a roll of theother bank or row. That is, the webalternately contacts the rolls of thetwo banks or rows so that first one of its sides, and then the other,contacts with the rolls.

As is well known, a paper web has a felt side and a wire side. Thelatter is that side next to the Fourdrinier wire as the paper is formed;the former is the side next .to the felt. The wire side of the-paper isrelatively smooth as compared with the felt side, wherefor there is adifference in the rate of drying between the two sides. That is, therelatively smooth or wire side of the paper contacts more perfectly withthe drying cylinders than does the less smooth or felt side with theresult that there is a difference in the drying rate which producespaper having unlike surfaces. To overcome this. various subsequentoperations on the paper are necessary.

In the operations of dryers of the type referred to, it has been thecommon practice to divide the cylinders into groups or sections and toheat the rolls of the different sections at different temperatures butthis does not overcome the difference in the drying rate existingbetween the felt and wire sides of the paper.

According to this invention, however, the difference in the drying rateis overcome by heating some of the rolls of one bank at one temperatureand the adjacent rolls of the other row or bank at a differenttemperature. Then the paper travels alternately over rolls of a certaintemperature and rolls of a different temperature.

; The temperatures are so controlled, according of a temperature higherthan that of the other cylinders with which the other or faster dryingside of the paper contacts. This facilitates the producing of paperwhich is substantially uniform on both sides; that is paper having moreuniform characteristics on opposite sides.

Various other novel objects and advantages or" the invention will beobserved from the following description of the present preferred formthereof, reference being had to the accompanying drawing wherein:

The figure is a small scale diagrammatic elevational view of a. dryingapparatus embodying certain novel features of the invention.

Now by reference to the drawing more in detail, the invention will befully described.

The dryer of the type to which the invention relates includes upper andlower banks or rows of cylinders or drums, commonly called cans. Thecylinders are hollow and are mounted for rotation so that a web Prepresented by dot-dash lines is carried alternately over a roll of theupper bank and over a roll of the lower bank and thereby through themachine in the direction of the arrow at. a i

A heating medium such as steam is delivered into the cylinders and thecondensate l ads from the rolls. Sometimes the steam is delivered intoone end of the cylinders while the condensate is taken out at the otherend and in other cases the steam and condensate return are at the sameend of the cylinder.

Suitable stufling boxes and connections are provided to facilitaterotation of the cylinders and form no part of the present invention, Forclearness, as will appear, the drawing shows the heating medium pipes atone end of the cylinders while the return, or condensate, pipes are atthe other.

According to the invention, a small number of the rolls such as 2 of theupper bank at the wet end of the dryer are operated at a differenttemperature than that of a plurality of adjacent rolls such as 4 of thelower bank. I

This is accomplished by the provision of separate headers 6 and 8tosupply the heat to the upper and lower cylindera The headers 5 and 8are connected by pipes' Ill and It to a main supply pipe l3 carrying theheating medium such as steam. Valves l4 and IS in pipes i9 and! controlthe flow of steam into the headers 6 and B. The headers 6 and 8 areconnected to the cylinders 2 and 4 by pipes I8 and 20. v Other drainageheaders 22 a'nd 24 are connected by pipes 26 and 28 to the cylinders'andthese headers are provided for the condensate. '55

They are connected, as by pipes 30 and 32, to a drainage system inassociation with which there may be means such as a vacuum pump to bringabout a low pressure condition.

As stated, the valves Ill and I! control the flow of steam to thecylinders so that the upper rolls may be operated at diiferenttemperatures than that of the lower rolls. The temperature of one groupof rolls may be relatively greater or less than that of the other group,and either the upper or lower group may carry the relatively highertemperature, depending upon the type of paper being handled, the dryingeffect necessary or desired, and other variable factors.

As an example, a certain type of paper may enter the dryer so that itsrelatively smooth wire side contacts with the upper rolls while itslower less-smooth side, which requires relatively more heat, contactswith the lower rolls. Under these conditions the lower rolls may beoperated at the desired and necessary higher temperature relative tothat of the upper rolls by controlling the fiow of steam to headers 8and I.

In this way, at the wet end of the dryer where the initial drying of thepaper takes place it is possible to provide the diflerence intemperature of the upper and lower rolls in order to overcome thedifilculties and objections inherent when there is a difierence in thedrying rate of opposite sides of the paper. I

- Other upper cylinders 3 and 3' and lower cylinders and 5' may beprovided. Of course, there may be any desired number of cylinders forsupporting and acting on the paper.

The rolls 3 and 5 constitute one group or section and the rolls 3' and5' constitute another group or section. The rolls may be arranged ofcourse to provide a desired number of sections.

Steam supply headers 40 and 42 are connected by pipes 44 and 46 whilesteam is carried to the cylinders by pipes 48 and ill. Control valves 52and 54 in pipes 44 and 46 control the flow of steam into the headers.

Return headers 58 and BI are connectedto the cylinders by pipes 80 and62 and pipes such as 64 and 86 are provided for drainage and maybeconnected to a vacuum pump or the like.

The valves ,18, 52 and 54 may take any form desired but will preferablybe such as will control the flow of steam within relativelynarrow limitsto thereby facilitate the accurate temperature control desired. They maybe of the thermostat type arranged to operate on temperature changes.

To that end it has been found desirable tha the valves be controlled intheir operation by the temperature of the condensate in the headers andthis may be accomplished by means of a temperature-sensitive substanceoperatively associated with the return headers and carried by conduits68, Ill, 12, and II which are connected to the control valves. A valveapparatus 'of the general type disclosed in United States Letters Patentto Lear 1,965,552 and dated July 3, 1934, with the necessarymodifications will sumce for this part of the invention.

Thus it will be seen that the paper to be dried isinitially led overcylinders of diflerent temperatures in such a way that opposite sidesthereof alternately contact with cylinders of diii'erent temperaturewhereby the difl'erence in the drying rate or ability to dry of theopposite sides of the paper is overcome or at least largely obviated.

while'I have described the invention in great detail and with respect toa preferred form thereof, it is not desired to be limited thereto sincemany changes and modifications may be made therein without departingfrom the spirit and scope of the invention. What it is desired to claimand secure by Letters Patent of the United States is:

1. The method of drying paper which consists in, contacting oppositesides of a web of-paper alternately with the cylinders of upper andlower spaced banks of cylinders, maintaining a certain portion of thecylinders of the lower bank of cylinders at a certain temperature and aportion of the cylinders of the upper bank adjacent to said certainportion of the lower bank with which the webfirst contacts at adiiferent temperature and maintaining other subsequent cylinders of thebanks which are adjacent one another at substan tially the sametemperature.

2. The method of drying paper which consists in leading a web ofpaper-into the leading in end of a dryer including spaced upper andlower rows of hollow drying cylinders so that said web has its oppositesides contacted alternately with cylinders of the upper and lower rowsof cylinders, maintaining a certain number of the cylinders of one rowat substantially one certain temperature and adjacent cylinders of theother row at substantially a diiferent temperature, whereby one side ofthe web contacts cylinders of one temperature and the other side of saidweb contacts cylinders of a d'iflerent temperature.

3. The method of drying paper which consists in, leading a web of paperinto the leading in end of a dryer including spaced upper and lower rowsof hollow drying cylinders so that said web has its opposite sidescontacted alternately with cylinders of the upper and lower rows ofcylinders, maintaining. a certain number of the cylinders of one row atsubstantially one certain temperature and adjacent cylinders of theother row at substantially a different teml perature, whereby one sideof the web contacts cylinders of one temperature and the other side ofsaid web contacts cylinders of a different temperature, and inmaintaining subsequent cylinders of the upper and lower rows atsubstantially the same temperature.

4. In the drying of a running matted paper web the opposite sides ofwhich have diflerent heat transfer characteristics, the method ofalternately but not simultaneously applying heat to the opposite sidesof the running web in such a manner that the quantityof heat supplied toone side of the web during each of a series of applications of heat tothat side is less than the quantity of heat supplied to the other sideof the said web during the next preceding application of heat to thesaid other side to produce a sheet which is substantially free oftendency to curl.

5. In the drying of a running matted fibrous web the opposite sides ofwhich have different to the other side of the said web to producethedesired relative drying of the two s des to obtain a sheet substantiallyfree from tendency to I curl.

6. In the drying of a running matted paper web having a smooth side anda rough side, the method of alternately but not simultaneously heatingthe two sides of the web, and supplying heat to the rough side at a.temperature suflicient- 1y greater than that at which heat is suppliedto the smooth side to cause the.desired drying of the respective sidesof the web.

7. In the drying of a running matted paper web having opposite sideshaving difierent heat transfer characteristics, the method comprisingweaving the running web over successive drying cylinders alternatelyheating opposite sides of the running web, and maintaining relativetemperatures oi drying cylinders heating one side of the web higher thanthe relative temperatures of related drying cylinders heating the otherside of the web to dry the respective sides of the web as desired.

GEORGE S. CARROLL.

